EXPRESSION AND FUNCTIONAL-ROLE OF 1F7 (CD26) ANTIGEN ON PERIPHERAL-BLOOD AND SYNOVIAL-FLUID T-CELLS IN RHEUMATOID-ARTHRITIS PATIENTS

The expression and the functional role of the CD26(1F7) T cell surface molecule, an ectoenzyme which seems to represent a functional collage n receptor of T lymphocytes and to have a role in T cell activation, w ere analysed in both peripheral blood (PB) and synovial fluid (SF)T ce ll samples from patients with active and inactive rheumatoid arthritis (RA). Although patients with active disease displayed higher percenta ges of PB CD26(+) CD4(+) T cells than inactive RA and control subjects , CD26 antigen expression on RA SF T lymphocytes was low. The anti-1F7 binding to the T cell surface, that led to CD26 antigen modulation an d enhancement of both IL-2 synthesis by, and H-3-TdR incorporation of, anti-CD3- or anti-CD2-triggered PB T cells in RA and control subjects , was unable to affect significantly both expression and functional ac tivity of RA SF T lymphocytes. Since the 1F7 antigen spontaneously rea ppeared on the surface of unstimulated SF T cells after 2-5 days of cu lturing, the low 1F7 antigen expression of anti-1F7 in the SF T cell c ompartment may be the result of in vivo molecule modulation exerted by the natural ligand in the joint, with important implications for T ce ll activation and lymphokine synthesis.